Range control system



Patented Dec. 3, 1935 PATENT OFF-ICE RANGE CONTROL SYSTEM- Herman M. Biebel, Oakmont, Pa, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,a corporation of Pennsylvania Application March so, 1934, Serial No. 718,276 11 Claims. (01. 219-20) My invention relates to electric ranges and more particularly .to temperature control systems for range ovens.

An object of my inventionis to provide a relatively simple and inexpensive combination of elements for controlling the temperature in an oven chamber. V

Another object is to providea relatively simple thermo-electric system of temperature control for an oven chamber permitting of obtaining any one of a number of difi'erent temperature cycles in the chamber, at the will of an operator.

1 Other objects of my; invention will either be specifically pointed outherelnafter or will be evident from the following description of the device or system embodying my invention and of its operation.

In practicing my invention, I provide a pair of contactors, one of these being a singleecycle contactor and the other being a plural-cycle contactor, a. single thermal actuable element actuble byvariations in chamber-temperature and two resiliently-connectedcontact members moved by the thermal element. The respective contactors 15 may be rendered eifective or ineflective as desired.

In the accompanying single sheet oi drawing:

Figure 1 is a schematic view of a combination of control elements embodying my invention;

Fig. 2 is a similar view of a modification em-.

30 bodying my invention; and,

,Fig.'3 is a similar view of another combination of elements and system embodyi g y invention. I

In the cooking of certain foods; particularly :5 meat, roasts, it is desirable that the exterior surfaceof the roast be seared at a relatively high temperature in order to cause the juices to remain within the roast itself during the remainder of the cooking operation, after which the cooking .41) is eifected at a substantially constant and relatively lower'temp'erature. For illustrativepurposes, the peak or searing temperature may be considered as on the order of 500 F., while the lower sustained or maintained temperature may be on the order of 300 F.,although, in order to make the system or more general application in cooking, this temperature should be adjustable within relatively wide limits, and at least down to boiling or simmering temperature. One of the time-temperature cycles which it is desired to obtain by the use of my system is, therefore, a momentary peak temperature on the order of 500 F. or over, and then a reduction 55 to a lower maintained temperature on the order of 300 F. for a length of time suflicient to properly cook the meat to the desired degree.

In the ordinary manually controlled range or. stove, the operator will provide by any suitable means, the initial high temperature required to 5 sear the meat and willthen arrange to subject the meat to the lower maintained temperature. This means an estimate on the part of the operator as to the length of time sufilcient to properly sear the roast. However, the use of the 1 system embodying my invention depending primarily upon the temperature in the oven chamber, does away with the need on the part of the operator'for estimating or otherwise determining the length of time required for searing a piece of 15 meat. It is obvious, of course, that a small roast, say on the order of three to five pounds, will be seared more quickly than a roast on the order of 15 lbs. or so.

Reference is here made to applicant's copend- 20 mg applications relating to similar subject-matter, Serial Nos. 718,272, 718,273, 718,274, 718,275 and 718,277 and to an application of F. S. Wheeler, Serial No. 718,278. all filed concurrently herewith.

Referring first to Fig. 1 of the drawing, I have there indicated an oven chamber H as enclosed by suitable walls l3 and an electric heating element ii of such capacity that it can raise the temperature within the chamber H to the dedesired relatively high temperature within a reasonable time, irrespective of the quantity of food located in the oven chamber. Inasmuch as the details of construction of the oven walls and oi the heating element constitute no part of my present invention, I have shown these schematically only. a

The heating element 15 is to be energized from a suitable source of supply of electric energy indicated by supply circuit conductors L1 and In, respectively, a main manually-operable switch II, which may be of any suitable or desired type, such as a snap switch, being provided for actuation by. an operator. 7 I

As it may, under certain circumstances, be desirable' to provide time-controlled means for starting and stopping the energization of the heating element in a manner well known in the art, I may provide a clock 19 comprising circuitcontrolling contacts therein, and in order to render the clock effective or ineffective, I may provide a manual switch 2| connected in parallel therewith.

'Means for controlling the energization of the heating element It and, thereioreof the tem- 2 perature in the oven chamber II, includes a single-cycle contactor II and a plural-cycle contactor II. The single cycle contactor II includes an actuating coil 21, an armature core II energized thereby, a main contact bridging member II, an auxiliary contact bridging member II, and

' fixed contact members II and II respectively adapted to engage withand be disengaged from the cooperating contact bridging members.

The plural-cycle contactor II includes an actuating coil II, a movable core II, a contact bridging member II and fixed contact members II cooperating with the contact bridging member.

Contacts II and the cooperating bridging member II are connected in series circuit relation with the heating element II one of the contact members. being connected to supply circuit conductor Ll while the other end of element II is connected to supply circuit conductor Ls. Oneofthecontactsllisalsoconnectedto conductor In. the bridgins member II and the other contact member being connected in series circuit with heating element II, so that the two circuit controlling pas-in of the respective contactors are connectedin parallel circuit with each other and in series circuit with the heating element II to severally or individually control the energizationof the heating element.

I provide further a single thermally actuable element "shown in Fig. l of the drawing as being constituted by a bimetal spiral, one end of which is fixed and the other end of which is operatively connected to a first contact arm II pivotally mounted on a suitable pivot pin. I provide a second contact or contact arm II resiliently operative'ly connected to the first contact or contact arm by a spring II. Upon expansion movement of the thermal member the first contact'or contact arm is directly actuated while the secondcontact or contact arm is indirectly actuated, and it is obvious that if the second contact arm is stopped at any point in its pivotal movement, the first contact arm may still turn. I have not shown any specific details as to the construction and arrangement of the bimetal spiral and of the two contact arms as any suit able or desired construction effective for the intended purpose can be utilized, and I consider it necessary only to show and describe sufilcient structure whereby to accomplish the desired pur- Means cooperatingwlth the two movable contacts include a maintained-temperature stopcontact II which is also shown generally only, and is to be understood as being so designed, constructed and located as to be adjustable within the desired temperature limits, and a peaktemperature contact II which is to be understood as being also adjustable. Peak temperature contact I1 is electrically" connected'to one terminal of coil II, the other terminal thereof being connected to a fixedcontact of a normally open switch II which may be of the so-called start push-button" type. The second contact bridging member II of contactor II is so connected in circuit with the manually actuable switch II and the coil 21 thereof as to provide a holding circuit for the coil, in a manner now well known in the art. Contact member II is connected in series circuit with coil II of contactor II, the circuit of this cell including a manually actuable switch II.

It will be noted that the thermally actuable plural arm switch of Fig. l of the drawing operates to deenergize the respective contactors b! short-circuiting their actuatin coils, and in order to reduce the current traversing the thermally actuable switch and its circuit I provide a single current limiting resistor II in a manner 5 well known in the art.

Referring now to Fig. 2 of the drawing, I have there illustrated a modified form of control system embodying my invention as applied to an oven chamber I I having a heating element II op- 10 eratively associated therewith. I provide a thermally actuable element II, here shown as a bimetal spiral and two contacts or contact arms I1 and II, respectively, adapted to be actuated in a counter-clockwise direction by the thermal 15 elanent upon a rising temperature and resiliently connected by a spring II. To avoid imdue stress of the bimetal spiral II, the end thereof is connected through a spring II with arm or contact II.

Arm II is adapted to normally engage an adjustably-mounted stop contact II which is connected in series circuit with the actuating coil of a contactor II, it being noted that In this system the contactors are deenergiaed by opening 23 the energizing circuit through the contactor coil. A second adjustably mounted contact II cooperates witharm II to control the circuit of a contactor II through the coil thereof, said circuit including also a manually actuable switch II.

It will be noted that contactor II Isa pluralcycle contactor and as it is desired that contactcr 11 shall be a single-cycle contactor only. that is, that after having been moved to its open position, it'will remain in that position imtiltl manually released by an operator, I provide a hook II operatively associated with the moving parts of contactor II and particularly secured to the brid ing member thereof, which is adapted to be engaged and held by a latch I1 pivotally 4i mounted and pressed by 'a spring II against the hook lug II, its counterclockwise turning movement being limited by a stop pin II. A manually adjustable push rod II is provided to effect release of the latch'I'I from hook II when de- 43 sired. 7

Referring now to'Pig. 8 of the drawing, I have there-illustrated a still further modffication'of a system embodying my invention as applied to an oven chamber II having a heating element .23 II associated therewith. I provide. as before. two contactors, a single cycle contactor II'and a plural cycle contactor II, which severally control the energization of heating element II and are, therefore, connected in parallel particularly 5 insofar as their circuit controlling elements are concerned.

Means for controlling the two contactors II and I1 include a thermally actuable element here shown as a bimetal strip II having its illustrated CJ left-hand end thereof mounted on a suitable fixed base, the free end thereof having a suitable spring contact member III associated therewith which is adapted to engage with and be disengaged from an adiustably mounted contact III. Contact (#5 member III is connected to one terminal of the actuating coil of contactor II, a manually actuable switch III being also connected in this circuit, so that if switch III is closed and contact spring III is in engagement with contact III, the T7) actuating coil of contactor I1 is energized through a circuit shown as closed in the drawing. The contact member III may be called the maintained-temperature contact member.

A peak-temperature contact means is also pro- 75 vided and is actuable by the bimetal member 99, thismeans including a small switch arm I91, the illustrated left-hand end of which is pivotally mounted on a suitable support and initially engaging a contact member I99 which is connected through a normally open and manually closable switch I to the actuating coil of contactor 95. A rod 3 extends through an opening in bimetal strip 99, and has its lower end pivotally connected to switch arm I01 and has its upper end externally screw-threaded to receivea knurled nut H5 thereon. The nut H5 can be adjusted axially of the rod I 3 to thereby also vary the chamber temperature at which the bimetal bar moving in a counter-clockwise direction-with increasing chamber temperature will actuatethe same to open or disengage arm I91 from contact I9 9.

As shown in Fig. 3 of'the-drawing, the single cycle contactor 95 is providedwith a holding circuit in cooperation with manually actuable' switch I, in a manner well known in the art,

and it is thought unnecessary to further apply ter having been caused thereby reference numerals to partsof the system.

The manually actuable switches 59 of Fig. 1 and Ill of Fig.3 with the holding circuits of which they forma part, and the latch 81 of Fig. 2 form, means for preventing reclosing of the corresponding contactors by the operation of the thermally actuable switches controlling them afto move into the the respective details and open position.

Referring now to Fig. 1 of the drawing, let it be assumed that an operator desires to cook a piece of meat by subjecting it first to a gradually increasing temperature until a predetermined peak temperature is reached, and to thereafter subject it to a sustained or maintained lower temperature Let it be assumed that switch I! has been closed and that it is not desired to use the time clock so that switch 2| is also closed. Switch 5| is moved to its closed position and switch 59 is also momentarily closed, whereby the various parts of the system will be in the position shown in Fig. 1 of the drawing, it being assumed that the oven chamber temperature is substantially that of the room. The movement of the bimetal element 41 will be such as to turn the contacts or contact arms 49 and 5| in a clockwise direction upon increase of temperature.

It will further be. evident that since both con tactors 23 and 25 have been properly energized, thecont rol of heating element I5 is eflected by the two contactors in parallel circuit relation with each other.

After a certain length of time, depending upon the various constants of the system, the temperature in oven chamber II will reach a predetermined lower temperature of the maintained temperature at which time arm 5| will engage stop contact 55, whereby coil "of contactor 25 is short-circuited and the This results in the disengagement of bridging member 43 from its cooperating contacts, but since contactor 23 is still energized, current will still traverse heating element I5 and will continue to traverse it until, with. further increase in the chamber temperature, contact arm 49 is moved into engagement with stop contact 51. The result of this engagement is that contactor 23 isdeenergized by reason of the short circuit of its coil 21. e The heating element I5 is, therefore,

substantially that.

deenergized and the temperature in chamber II will therefore gradually decrease.

Even though at a certain temperature slightly below the peak or maximum temperature, contact arm 49 is disengaged from contact 51, no change in position of contactor 23 can occur because of the opening of the holding circuit thereof. The temperature in the chamber will, therefore, continue .to decrease until at a certain lower temperature (which may be assumed for illustrative purposes to be 300 F.), arm 5| is disengaged from contact 55, whereupon coil 39 is re-energized, the contactor, therefore, closing its circuit to re-energize heating element l5. This results in again increasing the temperature in the oven chamber and at a certain slightly higher temperature, arm 5| is again caused to engage with contact 55, deenergizing the contactor coil and the circuit controlled by contactor 25. This intermittent sequential energization and deenergization of the contactor 25 and, therefore, of heating element 5 will maintain a substantially constant average temperature in the cooking chamber and will continue as long as the main circuit is energized, which time may be terminated either by the clock or by the operator opening main switch II.

It will be noted that I have provided a yielding connection between arms 49 and 5| so that even though arm 5| engages stop contact 55, arm 49 may still be moved in a clockwise movement until it engages its cooperating contact member, in the manner set forth.

If it should be desired to obtain a peak temperature cycle only, this can be done by the operator opening switch 6| to thereby render ineffective contactor 25. Upon energizing the circuit, as was hereinbefore stated, by the momen temperature cycle only this can be done by the operator closing switch 6| but not actuating switch 59 momentarily. The control of the heating element I5 is now effected by contactor 25 alone in the manner already set forth hereinbefore, and a substantially constant average maintained temperature will be provided in the oven chamber for as long a time as may be desired by the operator.

Referring now to Fig. 2 of the drawing this modified form of system operates in substantially the same manner as was hereinbefore set forth for the system shown in Fig. 1 of the drawing. If, upon closing main switch I! and by-pass switch 2|, the operator closes pushes on push rod 93 to release the movable parts of contactor 17, a combination peak and maintained temperature cycle will be obtained. If the operator does not push on push rod 93 to rebe obtained.

Referring to Fig. 3 of the drawing, bimetal bar 99 turns in a counter-clockwise direction upon increase of temperature in oven chamber II, and if switch 93 and in circuit with the respective contactor switches i1 and ii are closed, as well as switch I", and switch I i i momentarily only, a peak and then amaintained temperature cycle will be obtained. Upon the temperature in the chamber ii reaching a certain vaiu the spring will be disengaged from contact I, thereby deen the coil of contactor l1. However, energ'isation of the heating element continues by reason of the closed position oi contactor to. At a certain higher temperature nut II is engaged bythebimetalbarfltomoveswitchbar illto open position, thereby deenergising contactor ll. By reason of the holding circuit provided for conreducedto avalue whereswitcharm ill is again in engagement with contact I. It is only when spring arm lli reengagee contact III to thereby contactor I that heating element II is again energized and the same intermittent sequentialenergisation and deenergiaation of contactor l1 and, therefore, of heating element II, is effected as has already been described.

If it is desired to obtain a peak temperature cycle only, switch I ismovedtoits openpomtion by the operator, and switch I ii is closed momentarily and if a maintained temperature cycle only isdesired. switch lllisclosedandswitch I ll isnot actuated momentarily to its closed position. The operation of the various parts of the systemis the same as was hereinbefore set forth for the other figures of the drawing.

The device and system embodying my invention thus provides relatively simple, easily manufactured, inexpensive and readily installed means for obtaining any one of a number of diilerent timetemperature cycles on the part of an operator in an electrically heated oven by purely thermo-electric means.

the device and without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

for, means for obtaining, a peak temperature and then a maintained lower temperature cycle in the cooking chamber, said means including a single-cycle contactor controlling the energization of the heating element, a plural-cycle contsctor controlling the energisationof the heating element, conductors connecting said contactors in parallel with each other, a pair of spaced contact terminals individually connected coils and thermally-actuabie plural contact means responsive to chamber temperature cooperating with the pair of spaced contact terminals to control the contaciors, the first of the plural contact means initially cooperatin with the contact in the circuit of the plural-cycle contactor coil to eflect opening of the plural cycle contactor, the second of the plural contact means then cooperating with the contact terminal in the circuit of the single-cycle contactor to effect deenergization of the heating element at the desired peak temperature. the first contact means thereafter cooperating with the plural-cycle contactor to intermittently sequentially energize and deenergize the heating element.

appliance including 2. In an electric cooking a cooking chamber and a heating element therefor, a first contactor for controlling the energisetion of the heating element. means operatively associated with the first contactor to cause it to remain in open position after it has been moved 5 a second contactor for conment actuabie in response to variations in chamher temperature, a first contact arm directly actuated by the thermal element, a peak temperature contact adapted to be caused by the first electrically connected to the coil of said first contactor, a second contact arm resiliently connected to said first contact arm, a maintained-temperature contact adapted to be engaged by the second contact arm at a certain lower chamber temperature and electrically connected to the coil of the second contactor, engagement of the second contact arm with the maintained temperature contact causing opening of the second contactor, the first contactor continuing energization of the heating element until the first contact arm engages the peak temperature contact, after which the second contactor intermittently sequentially energizes and deenergizes the heating element by reason of the cooperation of the second contact arm and the maintained temperature contact.

3. In an electric cooking appliance including a cooking chamber and a heating element therefor, a pair of parallel connected contactors for controlling the energiaation of the heating element, a pair of spring-connected contact arms actuated by a single thermal element in accordance with variations in the chamber'temperature, a high-temperature contact and a lower maintained-temperature contact adapted to be operatively engaged by the respective contact arms 40 in predetermined sequence, conductors connecting the respective contacts to the contactor coils and means operatively associated with that contactor having the high-temperature contact connected thereto to cause it to remain in open position after it has been moved into such position.

4. In an electric cooking appliance including a cooking chamber and a heating element therefor, means for controlling the energization of the heating element to obtain a peak temperature and then a maintained lower temperature cycle in the cooking chamber, said means including a single-cycle contactor and a plural-cycle contactor electrically connected in parallel with each other for controlling the circuit of the heating element, a single thermal element subjected to the chamber temperature, a pair of spring-connected contact members actuated by the thermal element and contacts individually engageable by the respective contact members and electrically connected to the respective contactor coils. whereby the single-cycle contactor initially controls the energization of the heating element to obtain a peak temperature and the plural-cycle contactor thereafter controls the energization of the heating element to obtain a maintained lower temperature in the cooking chamber.

5. A device as set forth in claim 4 which ineludes means for rendering the two contactors o individually eiiective and ineffective at the will of an operator.

6. A device as set forth in claim 4 in which the circuit of each contactor coil includes a manually actuable switch for rendering the two contactors individually effective and ineflective at the will of an operator. a

7. A device as set forth in claim 4 in which the engagement of the contact arms and the contacts short circuits the cooperating contactor coils.

8. In an electric cooking appliance including a cooking chamber and a heating element therefor, means for obtaining a peak temperature and then a lower maintained temperature in the cooking chamber, said means including a first and a second contactor electrically connected in parallel and controlling the energization of the heating element, means operatively associated with said second contactor to cause the contactor to remain in open position after having been moved into such position, a circuit for each of the contactor coils including a contact terminal, a thermally-actuable plural-contact means responsive to chamber temperature adapted to cooperate withthe contact terminals to control the contactors, engagement of the first of said thermally actuable contacts with the contact terminal 01' the circuit of the first contactor coil effecting opening of the first oontactor and engagement of the second contact with the contact terminal in the circuit of the second contactor coil causing deenergization oi the heating element, the first thermally-actuable contact thereafter cooperating with the contact terminal in the circuit of the first contactor coil to intermittently sequentially energize and deenergize the heating element.

9. A device as set forth in claim 4 in which the means for rendering ineifective the single cycle contactor is a manually releasable mechani- 5 cal latch for the contactor.

10. A device as set forth in claim 4 in which the means for rendering inefiective the single cycle contactor includes a holding circuit for the contactor and a. manually actuable switch.

11. In an electric cooking appliance including a cooking chamber and a heating element there for, a pair of parallel connected contactors for controlling the energization of the heating element, a pair of spring-connected contact arms actuated by a single thermal element in accordance with variations in the chamber temperature,

a high temperature contact and a lower maintained-temperature contact adapted ,to be operatively engaged by the respective contact arms in predetermined sequence, conductors connecting the respective contacts to the contactor coils and means operatively associated with that contactor having the high-temperature contact connected thereto to prevent reclosing thereof by the action 2 of the thermal element and the cooperating contact and contact arm after having been caused to move into open position thereby.

HERMAN M. BIEBEL. 

